Civil Rights
Movements, leaders, victories and the continuing fight for equality.
q2K BHP
Black History Portal
THE BHP WIRE —
HIDDEN TRUTHS
What's New!
Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
Innovation, patents, science, technology and world-changing contributions.
Pioneers, champions, Negro Leagues, records, activism and excellence.
Meet the people whose lives, choices and achievements shaped the journey.
Black towns, communities, institutions and places where history happened.
Moments that changed communities, movements, institutions and the nation.
In 1968 Shirley Chisholm became the first Black woman elected to the United States Congress. In 1972 she launched a campaign for the Democratic presidential nomination, breaking another political barrier.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
Marginal-zone B cells (MZ B cells) are noncirculating mature B cells that in humans segregate anatomically into the marginal zone (MZ) of the spleen[1] and certain other types of lymphoid tissue.[2] The MZ B cells within this region typically express low-affinity polyreactive B-cell receptors (BCR), high levels of IgM, Toll-like receptors (TLRs), CD21, CD1, CD9, CD27 with low to negligible levels of secreted-IgD, CD23, CD5, and CD11b that help to distinguish them phenotypically from follicular (FO) B cells and B1 B cells.[2][3]
MZ B cells are innate-like B cells specialized to mount rapid T-independent, but also T-dependent responses against blood-borne pathogens.[4] They are also known to be the main producers of IgM antibodies in humans.[5]
The spleen's marginal zone contains multiple subtypes of macrophages and dendritic cells interlaced with the MZ B cells; it is not fully formed until 2 to 3 weeks after birth in rodents and 1 to 2 years in humans.[6] In humans, but not rodents, marginal zone B cells are also located in the inner wall of the subcapsular sinus of lymph nodes, the epithelium of tonsillar crypts, and the sub-epithelial area of mucosa-associated lymphoid tissues including the sub-epithelial dome of intestinal Peyer's patches.[2] Human MZ B cells are also present in peripheral blood, suggesting that they recirculate.[7] However, in mice they seem to be noncirculating and only limited to follicular shuttling.[2]
In rodents, MZ B cells are recognized as IgMhighIgDlowCD21highCD23low population of B cells. They are furthermore distinguished by the expression of CD9[3] and CD27 (in humans).[2] In mice, MZ B cells characteristically express high levels of CD1d, which is an MHC class I-like molecule involved in the presentation of lipid molecules to NKT cells.[8] Unlike FO B cells, MZ B cells express polyreactive BCRs that bind to multiple microbial molecular patterns. Additionally, they express high levels of TLRs.[2]
In specimens where the tyrosine kinase for Pyk-2 has been knocked-out, marginal zone B-cells will fail to develop while B-1 cells will still be present. MZ B-cells are the only B-cells dependent on NOTCH2 signaling for proliferation.[9]
Similar to B1 B cells, MZ B cells can be rapidly recruited into the early adaptive immune responses in a T cell-independent manner.[9] The MZ B cells are especially well-positioned as the first line of defense against systemic blood-borne antigens that enter the circulation and become trapped in the spleen.[10] While large blood-borne antigens are captured by dendritic cells, circulating granulocytes or MZ macrophages, smaller blood-borne antigens may directly interact with MZ B cells situated on the exterior of the marginal sinus.[2][4] MZ B cells shuttle between the blood-filled marginal zone for antigen collection and the follicle for antigen delivery to follicular dendritic cells. In mice, it has been shown that these cells shear flow via the LFA-1 integrin ligand ICAM-1 and adhere or migrate down the flow via the VLA-4 integrin ligand VCAM-1. While CXCR5/CXCL13 signaling is required for MZ B cells to enter the follicle, Sphingosine-1-phosphate signaling is required for them to exit from the follicle.[11]
MZ B cells respond to a wide spectrum of T-independent, but also T-dependent antigens. It is believed that MZ B cells are especially reactive to microbial polysaccharide antigens of encapsulated bacteria such as Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis. TLRs often activate MZ B cells after recognizing microbial molecular structures in cooperation with the BCR.[7] These innate-like B cells provide a rapid first line of defense against blood-borne pathogens and produce low-affinity antibodies of wide specificity before the induction of T-cell-dependent high-affinity antibody responses. Therefore, MZ B cells may play an important role in the prevention of sepsis.[8] MZ B cells also display a lower activation threshold than their FO B cell counterparts, with a heightened propensity for plasma cell differentiation that contributes further to the accelerated primary antibody response.[2][12] They have been acknowledged as the main producers of IgM antibodies in humans.[5]
They are important for antibody-response toward invading pathogens and maintaining homeostasis via opsonization of dead cells and cellular debris.[5] Moreover, MZ B cells are potent antigen-presenting cells, that are able to activate CD4+ T cells more effectively than FO B cells due to their elevated expression levels of MHC class II, CD80 and CD86 molecules.[2][7]
Deficiencies of MZ B cells are associated with a higher risk of pneumococcal infection, meningitis and insufficient antibody response to capsular polysaccharides.[2][4]
In humans the splenic marginal zone B cells have evidence of somatic hypermutation in their immunoglobulin genes, indicating that they have been generated through a germinal centre reaction to become memory cells. While naive MZ B cells produce low-affinity IgM antibodies, memory MZ B cells express high-affinity Ig molecules. Besides unswitched cells (IgM+), class-switched B cells can be found in the human and rodent marginal zone (IgG+ and IgA+). In humans, MZ B cells express CD27, which is a member of the TNF-receptor family expressed by human memory B cells.[8]
Many of MZ B cell-receptors are self-reactive, which may be a factor that contributes to their expansion in some autoimmune diseases. On the other hand, aiding in the clearance of self-antigens is considered an important mechanism to prevent the development of autoimmune diseases. The role of expanded self-reactive MZ B cells has been observed on mice models of lupus, diabetes and arthritis.[7] However, their levels in human vasculitis are reduced.[5]
Marginal zone B cells are the malignant cells in marginal zone lymphomas, a heterogeneous group of generally indolent lymphomas.[13]
{{cite book}}: CS1 maint: multiple names: authors list (link)
{{cite journal}}: CS1 maint: multiple names: authors list (link)
{{cite journal}}: CS1 maint: multiple names: authors list (link)
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Marginal-zone B cells (MZ B cells) are noncirculating mature B cells that in humans segregate anatomically into the marginal zone (MZ) of the spleen and certain other types of lymphoid tissue. The MZ B cells within this region typically express low-affinity polyreactive B-cell receptors (BCR), high levels of IgM, Toll-like receptors (TLRs), CD21, CD1, CD9, CD27 with low to negligible levels of secreted-IgD, CD23, CD5, and CD11b that help to distinguish them phenotypically from follicular (FO) B cells and B1 B cells. MZ B cells are innate-like B cells specialized to mount rapid T-independent, but also T-dependent responses against blood-borne pathogens. They are also known to be the main producers of IgM antibodies in humans.
Nodal marginal zone B cell lymphoma (NMZL) is an uncommon form of marginal-zone lymphoma that can produce colonization of the follicles in the lymph node. It is a form of low grade lymphoma with similar incidence in men and women and a mean age of 61 years (range 26–92 years). It is often associated with Sjogren syndrome. It shows interfollicular infiltrate of monocytoid, centrocyte-like B cells that are 2–3× larger than small lymphocytes with partial/total effacement of lymph node architecture.
Marginal zone lymphomas, also known as marginal zone B-cell lymphomas (MZLs), are a heterogeneous group of lymphomas that derive from the malignant transformation of marginal zone B-cells. Marginal zone B cells are innate lymphoid cells that normally function by rapidly mounting IgM antibody immune responses to antigens such as those presented by infectious agents and damaged tissues. They are lymphocytes of the B-cell line that originate and mature in secondary lymphoid follicles and then move to the marginal zones of mucosa-associated lymphoid tissue (MALT), the spleen, or lymph nodes. Mucosa-associated lymphoid tissue is a diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body such as the gastrointestinal tract, mouth, nasal cavity, pharynx, thyroid gland, breast, lung, salivary glands, eye, skin and the human spleen. In 2016, the World Health Organization classified MZLs into three different types. Extranodal marginal zone lymphomas (EMZLs) are MZLs that develop in extranodal tissues. Most EMZLs develop in MALT and are often termed extranodal MZL of mucosa-associated lymphoid tissue or, more simply, MALT lymphomas. Splenic marginal zone lymphomas (SMZLs) are MZLs that initially are confined to the spleen, bone marrow, and blood. Nodal marginal zone lymphomas (NMZs) are MZLs initially confined to lymph nodes, bone marrow, and blood. While all of these MZL involve malignant B-cells, they differ not only in the tissues they involve but also in their pathophysiology, clinical presentations, prognoses, and treatments. MZLs represent 5–17% of all Non-Hodgkin lymphomas with the extranodal, splenic, and nodal forms accounting for 50–70%, ~20%, and ~10% of all MZLs. The three MZL subtypes occur more often in older people (age 65–68 years) and are indolent diseases that may, in people without symptoms, be initially treated by a watchful waiting strategy. However, NMZL carries a somewhat worse long term outcome than the other subtypes and any of the MZL subtypes may progress in a low percentage of cases to a more aggressive lymphoma, particularly diffuse large B-cell lymphoma. One of the most distinctive features of MZL is that many cases are associated with the persistent simulation of the immune system by the chronic inflammation that accompanies infections or autoimmune disease. MZL cases associated with certain infectious pathogens can be cured by treatment directed at the pathogens causing or associated with these infections.
Within the immune system, follicular B cells (FO B cells) are a type of B cell that reside in primary and secondary lymphoid follicles (containing germinal centers) of secondary and tertiary lymphoid organs, including spleen and lymph nodes. Antibody responses against proteins are believed to involve follicular B cell pathways in secondary lymphoid organs. Mature B cells from the spleen can be divided into two main populations: FO B cells, which constitute the majority, and marginal zone B-cells, lining outside the marginal sinus and bordering the red pulp. FO B cells express high levels of IgD, and CD23; lower levels of CD21 and IgM; and no CD1 or CD5, readily distinguishing this compartment from B1 B cells and marginal zone B-cells. FO B cells organize into the primary follicles of B cell zones focused around follicular dendritic cells in the white pulp of the spleen and the cortical areas of peripheral lymph nodes. Multiphoton-based live imaging of lymph nodes indicate continuous movement of FO B cells within these follicular areas at velocities of ~6 μm per min. Recent studies indicate movement along the processes of FDC as a guidance system for mature resting B cells in peripheral lymph nodes. Unlike their MZ counterpart, FO B cells freely recirculate, comprising >95% of the B cells in peripheral lymph nodes. The BCR repertoire of the follicular B cell compartment also appears under positive selection pressures during final maturation in the spleen. However, diversity is substantially broader than B1 B and MZ B cell compartments. More importantly, FO B cells require CD40-CD40L dependent TFH cell help to promote effective primary immune responses and antibody isotype switching and to establish high-affinity B cell memory.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
